The present invention relates to drive trains for vehicles and, more particularly to systems that reduce vibration in drive trains.
Most conventional vehicles are equipped with a drive train that transfers power and torque from an engine to wheels or tracks to propel the vehicle along a surface. Drive trains typically include an engine, a transmission, a driveshaft and an axle. The transmission provides sufficient gearing to propel the vehicle at desired speeds when power and torque are transferred from an engine to the transmission. The driveshaft connects the transmission to the axle to transfer power and torque from the transmission to the axle and subsequently to the wheels or tracks of the vehicle.
Many automotive manufacturers provide warranties that cover excessive wear or damage to drive train components under normal operating conditions. This is particularly true in the semi-truck manufacturing industry. Such warranties typically cover the various components of the drive train. Thus, it is an objective of the manufacturers to lengthen the life of the drive train to reduce costs associated with repairs done under warranty.
A significant cause of drive train damage and excessive wear is vibration. Vibration frequently is the result of drive train components being mis-aligned in operation. For example, the transmission and axle typically are positioned relative to one another so that the drive shaft rotates and communicates power and torque between the two at a prescribed design angle (or range of angles) to horizontal. When a vehicle is fully loaded, for example, when a semi-truck is loaded with a heavy trailer, the vehicle""s suspension compresses and the ride height of the vehicle (i.e., the height of the frame relative to some fixed point on the vehicle) changes. Consequently, the drive train components, which are secured to the frame, move relative to one another so that the angle of the driveshaft changes with respect to the prescribed design angle. In this condition, the driveshaft and other drive train components are misaligned and thus have a tendency to vibrate in operation. This vibration typically increases with higher vehicle speeds.
With increased vibration, the drive train components undergo excessive wear, and in some cases the components catastrophically fail. Such wear and failure is very costly. One attempt to reduce drive train vibration is implemented via a mechanical height control that measures the ride height of the vehicle. If the ride height changes when the vehicle is loaded, then the mechanical height-control returns the ride height to a pre-set, factory ride height by adjusting the suspension elements of the vehicle. Nonetheless, excessive vibration still may exist in the drive train due to the load in combination with other factors, such as engine torque, tire size and pressure, vehicle frame deflection, frame rake (i.e., the angle of the frame from the front of the vehicle to the back) and wind. Thus, even with mechanical ride height controls, drive trains still may be subject to costly repair and down time due to wear and damage caused by vibration.
The aforementioned problems are overcome in the present invention in which a control system senses vibration in a vehicle drive train and adjusts the ride height of the vehicle to reduce or eliminate the vibration. Preferably, the ride height is adjusted so that the drive train components are aligned within optional parameters to reduce or eliminate vibration.
In a preferred embodiment, the control system includes a control unit, a sensor and a module that adjusts the vehicle""s suspension and, thus, the vehicle""s ride height. The sensor measures vibration or torque, for example, transmission vibration or engine torque. The sensor may be a stand-alone sensor, or the control unit may communicate directly with the vehicle""s data communication bus to derive the vibration, torque and/or other information. The measurements of the sensor are relayed to the control unit, which determines if the measurements are abnormal. If the measurements are abnormal, the control unit activates the module to adjust the suspension so that the ride height of the vehicle changes. By adjusting the ride height of the vehicle, the angular relation of the drive train components, for example, the axle, the driveshaft and the transmission are realigned to effectively reduce or eliminate the abnormal vibration and/or torque.
In a more preferred embodiment, the module is a valve and the suspension includes air ride suspension elements. When the control unit determines abnormal vibration and/or undesirable torque variation (UTV), it opens and/or closes the valve to inflate or deflate the suspension elements and, thus raise and/or lower the ride height of the vehicle. Optionally, a height sensor feeds back height information to the control unit to monitor the adjustment of the ride height of the vehicle and more efficiently reduce excessive vibration and/or UTV. Further optionally, the control unit continues to monitor vibration and repeatedly adjust ride height until excessive vibration and/or UTV is reduced or eliminated.
In another embodiment, the control unit adjusts the ride height of the vehicle based on the speed of the vehicle. For example, when cruising speeds are detected, the control unit lowers the vehicle ride height via the module to reduce the vehicle""s profile and improve fuel economy. The control unit does this while monitoring vibration and/or torque to prevent an excess of either from developing.
These and other objects, advantages and features of the invention will be more readily understood and appreciated by reference to the detailed description of the invention and the drawings.